In a tilting apparatus of this kind know from German laid-open application DE-OS No. 24 32 248, the operating lever is held in place in a crank guided in the tilting body, and a drag lever articulated on the crank in turn displaces a locking device, by means of which the holder plate and tilting body can be connected firmly with one another or unlocked. The crank is disposed in a vertically movable release lever, by means of which a releasing pin of a longitudinally displaceable gas spring can be actuated. The gas spring is part of a chair column which is adjustable in height. This known lockable tilting apparatus can be used for so-called executive chairs, the seat of which can be inclined backward by a predetermined angle when the locking device is released. It is also known to use locking apparatuses of fundamentally the same design for chairs having a seat that can be tilted forward when the locking device is released. This latter application relates primarily to so-called secretarial chairs. Each of these tilting apparatuses is suitable for only one of these types of chair; that is, they are tiltable in only one direction.